that one of his sons, 26-year-old tamerlan had been killed in a shootout and other dzhokhar was being pursued "my son is a true angel." dzhokhar is a second year medical opportunity in the u.s. wexpted him to come and accomplished young man. and is a second year medical student, according to his father. >> we heard from his classmate as well. >> we'll take that to martha raddatz, our chief global affairs correspondent right now, martha, we're learning more and more about the suspects as the morning goes on now. we do know they are of chechen origin, one of the brothers had been here, the one still on the loose for about 12 years, his older brother for about five years, significant, perhaps, that his father still lives in russia in one of the russian republics could reinforce the idea that perhaps the young men did go back at various times. >> reporter: yeah, that's a surprise that the father still lives in russia because when they left chechnya apparently they moved to kazakhstan and dagestan after that and the youngest was born in kazakhstan. i don't know whether the mother is here.